How Much Aerobic Exercise is Enough?

Are there drawbacks to doing too much cardiovascular exercise?

Decades of research have made two things clear: Every bit of cardiovascular activity helps – even in spurts as short as 10 minutes – and more is almost always better.

Where experts are divided is on how to communicate the second message without discouraging people who are still struggling with the first.

And there are a lot of people struggling: Only a third of Canadians undertake the recommended minimum of 30 minutes of moderate exercise, four times a week – even though doing just a bit of activity reduces the risk of dying from heart disease and related conditions by a whopping 30 percent.

But what happens if you do more exercise than the government guidelines recommend? Paul Williams, a researcher in the Life Sciences Division at the Lawrence Berkeley National Lab in California, has been following a cohort of 120,000 runners since 1991, and has uncovered a pronounced “dose-response” relationship between aerobic activity and health: The more you do, and the more intensely you do it, the more benefits you reap.

The risk of everything from such big killers as diabetes, stroke and heart attack to less common conditions like glaucoma, cataracts and macular degeneration can be reduced by as much as 70 percent when you exceed the standard exercise guidelines.

So when it comes to cardio, the very first steps are the most important of all. Just don’t stop there.